玉米淀粉/羧甲基纤维素生物复合凝胶的制备及吸附行为研究

以玉米淀粉与羧甲基纤维素（CMC）为骨架，以丙烯酸（AA）、丙烯酰胺（AM）、2-丙烯酰胺基-2-甲基丙磺酸（AMPS）为单体制备复合凝胶，对复合凝胶材料进行表征。以亚甲基蓝（MB）为吸附质，考察复合凝胶吸附剂对阳离子染料吸附过程的动力学和热力学行为，分析阳离子强度、水体pH值、染料初始质量浓度等对吸附剂吸附性能的影响。结果表明：玉米淀粉-CMC-g-AA-AM-AMPS凝胶是一种表面多孔的吸附材料，其比表面积为24.939 7 m2/g，平均吸附孔径为8.668 2 nm。凝胶对MB的吸附过程与准二级动力学模型和Langmuir模型拟合较好，属于单分子层的化学吸附。阳离子对凝胶吸附MB有明显抑制作用，抑制效果为Al3+>Ca2+>Na+。随着离子强度的增加，抑制作用越明显。在投加量为0.1 g、温度为298 K、pH值为11.0、MB初始质量浓度为2 000 mg/L条件下，吸附剂最大吸附量达到1 938.82 mg/g、去除率为96.94%，能有效去除MB。     

GO/GA-g-PAMPS复合水凝胶的制备及阳离子染料吸附性能

以自制氧化石墨烯（GO）和阿拉伯胶（GA）、2-丙烯酰胺基-2-甲基丙磺酸（AMPS)为原料，采用一步水热反应法制备了GO/GA-g-PAMPS新型复合水凝胶，利用FTIR、XRD、SEM对复合水凝胶结构进行了表征。研究了GO浓度、溶液pH、染料初始浓度、吸附时间、吸附温度对阳离子染料亚甲基蓝（MB）和结晶紫（CV）吸附性能的影响。结果显示：水凝胶对阳离子染料具有较好的吸附效果，在GO浓度为0.3mol/mL，凝胶用量为0.05g，溶液pH为7，温度为50℃，染料初始浓度为200mg/L时，凝胶对MB和CV的吸附量和吸附率分别为395.68、381.70mg/g和98%、96%。凝胶经过5次循环使用后，对MB和CV的吸附率仍能达到82.6%和81.2%。吸附等温线和动力学研究表明，凝胶对MB吸附更符合Freundlich模型，对CV的吸附更符合Langmuir模型，准二级动力学模型能更好地描述两种阳离子染料的吸附过程。热力学研究表明水凝胶对两种染料吸附是自发、吸热和混乱度增加的过程。     

马来酸酐接枝纤维素超细纤维制备高容量可再生吸附剂

在静电纺丝制备出纤维素超细纤维（CSF）的基础上,利用马来酸酐（MAH）改性制备了新型羧基化吸附剂,接枝温度为100℃,时间为3h,MAH与CSF质量比为5：1,过氧化二苯甲酰（BPO）用量为7.5%时接枝效果最佳,取代基含量可达2.304mmol/g。通过SEM观察了纤维素超细纤维改性前后的形态分布和微观结构,通过酸碱滴定定量地测定了改性纤维素超细纤维（MAH-CSF）中的取代基含量,FTIR图谱分析定性地表明马来酸酐成功地接枝在了纤维素超细纤维上。从XRD和DSC谱图中得知MAH-CSF的晶型未发生变化但结晶度有所下降,马来酸酐改性提高了纤维素超细纤维的热稳定性。研究了CSF和MAH-CSF对亚甲基蓝的吸附性能,经马来酸酐改性后纤维素超细纤维对亚甲基蓝的吸附量从210mg/g提高到了306mg/g,这表明羧基化可极大地提高其对亚甲基蓝的吸附量。在低pH下,H⁺与亚甲基蓝间的竞染作用使得吸附剂的吸附量较小;随着吸附剂的去质子化,吸附量明显迅速增大;在pH大于5.5时吸附量增加趋势减缓。MAH-CSF与MB之间的离子交换作用使其具有更优良的吸附效果,吸附过程更适合用准二级动力学模型来描述。在超声波作用下吸附剂再生5次的吸附率达89%以上,这表明吸附剂具有很好的再生性。     

交联羧甲基纤维素的制备及对染料吸附性能的研究

酸催化下,取代度0.82的羧甲基纤维素钠(CMC)经固相加热反应,制备吸附材料交联羧甲基纤维素(CCMC)。研究反应条件对CCMC交联度、交联度对CCMC吸附碱性品红(BF)和亚甲基蓝(MB)性能的影响。结果表明,酸浓度对CCMC交联度影响最大,交联度0.39的CCMC的吸附性能最佳。以交联度0.39的CCMC为吸附剂,研究吸附条件包括固液比、染料初始浓度、pH、吸附时间对CCMC吸附性能的影响。20℃,固液比0.25 g/L条件下,CCMC对BF和MB的饱和吸附量分别为570 mg/g和540 mg/g。     

交联羧甲基纤维素的制备及对染料吸附性能的研究

酸催化下,取代度0.82的羧甲基纤维素钠(CMC)经固相加热反应,制备吸附材料交联羧甲基纤维素(CCMC)。研究反应条件对CCMC交联度、交联度对CCMC吸附碱性品红(BF)和亚甲基蓝(MB)性能的影响。结果表明,酸浓度对CCMC交联度影响最大,交联度0.39的CCMC的吸附性能最佳。以交联度0.39的CCMC为吸附剂,研究吸附条件包括固液比、染料初始浓度、pH、吸附时间对CCMC吸附性能的影响。20℃,固液比0.25 g/L条件下,CCMC对BF和MB的饱和吸附量分别为570 mg/g和540 mg/g。     

纳米多孔ZnO的制备及吸附性能研究

以硝酸锌和尿素为原料,采用水热法制备纳米多孔ZnO。通过X-射线衍射仪(XRD)、扫描电子显微镜(SEM)对所制备的纳米多孔ZnO进行成分和形貌表征,并将其用于吸附处理亚甲基蓝(MB)模拟工业染料废水,考察了溶液pH值、纳米多孔ZnO用量、MB溶液初始浓度对吸附效果的影响。结果表明:纳米多孔ZnO对MB有着较好的吸附能力;在室温20℃下,0.10g的纳米多孔ZnO对100mL初始浓度为10mg·L-1、pH值为12的MB溶液的吸附率达92.10%、平衡吸附量达9.21mg·g~(-1)。     

AM-g-CCMC树脂的制备及其吸附性能

以交联羧甲基纤维素(CCMC)、丙烯酰胺(AM)为原料,过硫酸钾为引发剂,N,N'–亚甲基双丙烯酰胺为交联剂,通过微波辐射法制备了吸水性树脂丙烯酰胺接枝交联羧甲基纤维素(AM–g–CCMC)。研究了溶液p H值、盐溶液浓度对AM–g–CCMC树脂吸水倍率的影响;同时考察了染料p H值、吸附时间、染料浓度、吸附剂浓度对树脂吸附量[对碱性品红(BF)和亚甲基蓝(MB)]的影响。结果表明,AM–g–CCMC对去离子水和浓度为0.154 mol/L的Na Cl,Ca Cl2,Fe Cl3溶液的最大吸水倍率分别为1 735,165,82,43 g/g;在20℃,浓度0.25 g/L条件下,AM–g–CCMC对BF和MB的最大吸附量分别为370 mg/g和323.4 mg/g。同时对该树脂的循环利用性能进行了初步研究。结果表明,吸附MB的AM–g–CCMC的再生效果略好于吸附BF的树脂。     

纤维素基纳米复合材料对亚甲基蓝的吸附及解吸性能

采用FTIR和SEM对纤维素-g-聚丙烯酸/丙烯酰胺/蒙脱土(LNC-g-PAA/AM/MMT)纳米复合高吸水性树脂的结构进行表征。研究亚甲基蓝染料的初始质量浓度、吸附时间、吸附温度和pH等不同条件下,对LNC-gPAA/AM/MMT吸附该染料吸附量的影响。此外,在最佳条件吸附饱和时,改变解吸时间、HCl浓度等研究LNC-gPAA/AM/MMT的解吸性能。结果表明:初始质量浓度为2 500 mg/L,120 min,30℃,pH=5时,LNC-g-PAA/AM/MMT的吸附量高达2 038.7 mg/g。整个过程很好地符合伪二级动力学模型和Langmuir等温线。在解吸时间120 min,HCl浓度0.05 mol/L时,解吸率高达73.16%。     

PAN纳米纤维膜的制备及其对阳离子染料的吸附研究

以聚丙烯腈(PAN)粉末为原料,N-N二甲基甲酰胺(DMF)为溶剂,制备PAN纳米纤维膜,根据纤维外貌、直径、孔隙率等探究纳米纤维膜的最佳PAN浓度。阳离子染料模拟印染废水,用PAN纳米纤维膜吸附阳离子染料,探究不同时间、不同初始浓度对亚甲基蓝(MB)吸附效果影响。结果表明:PAN浓度为10%时,纤维状态最佳; PAN纳米纤维膜的吸附率随着时间的增长先增大然后逐渐稳定,随MB质量浓度的增大先上升后降低。     

VMT/P(AMPS-co-AA)复合高吸水树脂的性能测试

研究了溶液pH、盐浓度对辉光放电电解等离子体引发合成的蛭石/聚(2-丙烯酰胺-2-甲基丙磺酸-co-丙烯酸) (VMT/P(AMPS-co-AA)) 复合高吸水树脂的溶胀行为的影响,考察了染料pH、吸附时间、染料浓度等因素对复合高吸水树脂吸附量的影响,同时对树脂的吸附-解吸性能进行了研究。结果表明, VMT/P(AMPS-co-AA)具有高吸水性、pH敏感性、盐敏感性以及高吸附性。该树脂在蒸馏水中的最大溶胀率达到822.4 g/g,对阳离子染料亚甲基蓝(MB)、结晶紫(CV)和孔雀石绿(MG)的吸附量分别可达2027.8, 2171.8和883.2 mg/g。在pH=6.5和25℃下,其对染料的吸附行为符合动力学准二级模型,该树脂还具有一定的吸附-解吸性能和重复利用性能。     

Adsorption behavior of cationic dyes on citric acid esterifying wheat straw: kinetic and thermodynamic profile

The kinetic and thermodynamic behaviors of cationic dye adsorption onto citric acid esterifying wheat straw (EWS) from aqueous solution were investigated. Two cationic dyes, methylene blue (MB) and crystal violet (CV) were selected as adsorbates. The kinetic and thermodynamic parameters of dye adsorption were examined with a batch system by changing various experimental factors (e.g. initial pH, EWS dosage, dye concentration, contact time, temperature). The MB and CV removal ratios came up to the maximum value beyond pH 4. The 2.0 g/L or up of EWS could almost completely remove MB and CV from 250 mg/L of dye solution. The adsorption percentages of MB and CV kept above 95% over a range from 50 to 350 mg/L of dye concentration when 2.0 g/L of EWS was used. The isothermal data followed the Langmuir model. The adsorption processes could be described by the pseudosecond-order kinetic model. The dual linear plots of intraparticle diffusion indicated that two intraparticle diffusion steps occurred in the dye adsorption processes. The thermodynamic study indicated that the adsorptions of dyes were spontaneous and endothermic. High temperatures favored the adsorption processes.     

Chitosan/polyaniline hybrid for the removal of cationic and anionic dyes from aqueous solutions

Nanostructured chitosan/polyaniline (CH/PANI) hybrid was synthesized via in situ polymerization of aniline in the presence of chitosan. The CH/PANI hybrid was characterized by FTIR spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The CH/PANI hybrid had a nanofibrous structure with an average diameter of 70 nm. This hybrid was employed as an ecofriendly and efficient adsorbent with high adsorption capacity for the removal of Acid Green 25 (AG) and methylene blue (MB) from aqueous solutions. AG and MB were used as anionic and cationic model dyes, respectively. The CH/PANI adsorbent showed high dependence on the pH of the medium with an excellent adsorption performance and regeneration manner. The kinetics and adsorption isotherms were studied. The CH/PANI hybrid follows the pseudo second-order adsorption kinetics and Temkin isotherm model for the adsorption of both AG and MB dyes. This assumes that the enthalpy of dyes molecules decreases with the adsorption on heterogeneous surface with various kinds of adsorption sites and as well as the ability to form multilayers of the dye. Also, intraparticle diffusion was found to play an important role in the adsorption mechanism. The maximum adsorption capacity was found to be 240.4 mg g⁻¹ of AG at pH 4 and 81.3 mg g⁻¹ of MB at pH 11. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47056.     

Use of sodium alginate biopolymer as an extracting agent of methylene blue in the polymer-enhanced ultrafiltration technique

In this study, the removal of methylene blue (MB) cationic dye from an aqueous solution was investigated using the polymer-enhanced ultrafiltration (PEUF) technique with sodium alginate (SA) as an extracting soluble polymer, in combination with an ultrafiltration membrane of regenerated cellulose with a 10 kDa molar mass cut-off. SA was characterized via Fourier-transform infrared spectroscopy and thermogravimetric analysis. For ultrafiltration studies, the washing method was used to evaluate various experimental variables, such as the pH, SA dose and initial MB concentration, and adsorption isotherms to identify the optimal adsorption conditions. Finally, the regeneration of the SA polymer was evaluated in five consecutive cycles of adsorption–desorption of MB. In the obtained characterization results, the structural composition of SA and the characteristic thermal stability of the polymer were verified. The PEUF results demonstrated that a retention capacity of 98% of the MB was realized at pH 8.0 using 0.025 g of SA at an initial optimal MB concentration of 50 mg L⁻¹. It is possible to observe that the Freundlich model better explain the interaction between the dye and the polymer surface. According to the results is demonstrated the regeneration capacity of the polymer and its subsequent reuse.     

Adsorption of Anionic and Cationic Dyes from Aqueous Solution on Non-Calcined Mg-Al Layered Double Hydroxide: Experimental and Theoretical Study

Non-calcined Mg-Al layered double hydroxide (LDH) with Mg/Al molar ratio of 3:1 was synthesized using the co-precipitation method. Sorption of anionic (acid blue 25 - AB25, reactive blue 4 - RB4), and cationic (methylene blue - MB) dyes by Mg-Al LDH form aqueous solution was investigated. The effect of solution pH, initial concentration, and contact time were investigated by batch adsorption experiments. The adsorbed amount increases with decrease in pH solution for AB25 and RB4. The cationic dye (MB) solution was insensitive to pH variation and also exhibited a low performance in the kinetic equilibrium studies. While anionic dyes were almost completely extracted from the solution, 90% of the methylene blue remained in solution. The equilibrium data were well described using the Langmuir-Freundlich model for RB4, AB25, and MB dyes with maximum adsorption capacity of 328.90, 246.10, and 43.48 mg/g, respectively. Finally, the mechanism of adsorption involving the dyes and LDH was evaluated using the Monte Carlo approach in the NVT ensemble. The results suggest that molecular simulation can be used to preview quantitatively the dye uptake. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.     

The removal of cationic dyes from aqueous solutions by adsorption onto pistachio hull waste

The efficacy of pistachio hull powder (PHP) prepared from agricultural waste was investigated in this study as a novel adsorbent for the elimination of dye molecules from contaminated streams. Removal of methylene blue (MB) as a cationic model dye by PHP from aqueous solution was studied under different experimental conditions. The selected parameters were solution pH (2–10), PHP dosage (0.5–3 g/L), MB concentrations (100–400 mg/L), contact time (1–70), and solution temperature (20–50 °C). The experimental results indicated that the maximum MB removal could be attained at a solution pH of 8. The dosage of PHP was also found to be an important variable influencing the MB removal percentage. The removal efficiency of MB improved from 94.6 to 99.7% at 70 min contact time when the MB concentration was decreased from 300 to 100 mg/L at a pH and PHP dosage of 8 and 1.5 g/L, respectively. The kinetic analysis showed that the pseudo-second-order model had the best fit to the experimental data. The Langmuir equation provided the best fit for the experimental data of the equilibrium adsorption of MB onto PHP at different temperatures. In addition, the maximum adsorption capacity increased from 389 to 602 mg/g when the temperature was increased from 20 to 50 °C. The thermodynamic evaluation of MB adsorption on PHP revealed that the adsorption phenomenon under the selected conditions was a spontaneous physical process. Accordingly, pistachio hull waste was shown to be a very efficient and low-cost adsorbent, and a promising alternative for eliminating dyes from industrial wastewaters.     

水热法合成二氧化锰及其对染料的脱色性能研究

采用水热法以十二烷基苯磺酸钠为模板合成二氧化锰,并研究水热温度对二氧化锰的结构和染料脱色性能的影响,以及样品投加量和染料溶液的pH对二氧化锰染料脱色性能的影响。结果表明:当水热温度为110 ℃时,得到2~8 μm球状γ-二氧化锰,对亚甲基蓝（MB）和罗丹明B（RhB）的脱色效果最好。当其投加量为6 g/L时,分别对50 mg/L的MB和RhB脱色率达到86.95%和76.07%。强酸和强碱条件下其对MB的脱色率有明显的提升,二氧化锰对MB的吸附过程符合Langmuir和Freundlich等温模型;强酸条件下其对RhB的脱色率有明显的提升,对RhB的吸附过程符合Freundlich等温模型。二氧化锰样品可循环使用,循环吸附3次后对MB和RhB的吸附量分别减少1.08 mg/g和2.66 mg/g。     

羧基酯化改性花生壳对染料废水的吸附

通过甲醇酯化法制备改性花生壳,用于吸附刚果红、次甲基蓝染料废水.考察了吸附时间、溶液pH值、初始浓度对吸附的影响及改性花生壳的再生.结果表明,在室温、刚果红在pH值4.16、次甲基蓝在7.45时,吸附效果最佳,经搅拌吸附120 min达到平衡,两染料最大吸附率分别为82.30％和90.84％,饱和吸附量分别为10.88 mg/g和11.82 mg/g.吸附符合一级动力学过程和Langmuir等温吸附模型.改性花生壳吸附效果较未改性花生壳明显提高,且可经0.5 moL/L NaOH溶液再生重复使用.     

Removal of methylene blue from aqueous solution by sorption on lignocellulose-g-poly(acrylic acid)/montmorillonite three-dimensional cross-linked polymeric network hydrogels

Batch lignocellulose-g-poly(acrylic acid)/montmorillonite (LNC-g-PAA/MMT) hydrogel nanocomposites were applied as adsorbents. The nanocomposites were characterized by FTIR, XRD, SEM, and TEM. The results showed that montmorillonite (MMT) could react with the monomers and change the structure of polymeric network of the traditional superabsorbent materials, an exfoliated structure was formed in the nanocomposites. The effect of process parameters such as MMT content (wt%), contact time (t), initial concentration of dye solution (C ₀), adsorption temperature (T), and pH value (pH) of the dye solution for the removal of methylene blue (MB) from aqueous solution were also studied. The results showed that the adsorption capacity for MB increased with increasing contact time, initial dye concentration, and pH value, but decreased with increasing MMT content and temperature. The adsorption kinetics were better described by the pseudo-second-order equation, and their adsorption isotherms were better fitted for the langmuir equation. By introducing 20 wt% MMT into LNC-g-PAA polymeric network, the obtaining hydrogel composite showed the high adsorption capacity 1994.38 mg/g and economic advantage for MB. The desorption studies revealed that the composite provided the potential for regeneration and reuse after MB dye adsorption, which implied that the composite could be regarded as a potential adsorbent for cationic dye MB removal in a wastewater treatment process.